When dimensioning the LORO-X DUOSTREAM cascade drainage with multi-storey drains, it must be taken into account that the drainage from each storey is added up in the collecting line (stream) which runs from top to bottom. As the outflow increases all the way down, the "lower" floor is of crucial importance in that it limits the overall performance of the stream.

In the following steps we would like to describe the procedure for the design of a system with multi-storey drains and pressing gravity flow using an example.

The calculation of the discharge in l / s can be done with the online calculation exactly as with conventional roof drainage for each floor.

Then the course of the line of stream 1 (main drainage) and stream 2 (emergency drainage) is described. The outflow QMain and QNot per floor is added up, the height of the downpipe is checked per floor (observe limit at least 2.5m!) And the length of the horizontal warping per floor is checked (observe limit max. 8m!).

Finally, the sum of the outflow per line is determined (note the limit of 4 l / s or 8 l / s per stream!).

Then the parts list for stream 1 and stream 2 is determined. One of the templates prepared by LORO can be used for this (linked next to this text). In the PDF you will find standard parts lists for warpage in the thermal insulation or above the sealing membrane.

These templates now only have to be adapted object-related, depending on the height of the downpipes and the length of the horizontal warps. Items with a blue background in the parts list must be counted several times depending on the number of floors.

If one of the mentioned limits cannot be adhered to, please contact LORO.

For a quick overview, we have summarized important design principles for the DUOSTREAM cascade drainage with pressing gravity flow in the adjacent PDF:

- The maximum outflow results from the sum of the line!
- Roof drain with gravity flow.
- Multi-storey drains with gravity flow drainage edge, gravity flow drainage outer pipe and pressure flow throughflow inner pipe.

- In the pressure-resistant downpipe a water-air column, controlled by measurement and calculation, builds up on each floor.
- Downpipes DN100 must have ventilation openings on each floor for ventilation to safely fill the downpipe without air inclusion.
- The diversion of the pressure-resistant downpipe with gravity flow diameter DN100 goes into the pressure-resistant draft pipe with pressure flow diameter DN50 with overpressure.

- Due to the high flow speed of the DN50 pipe, the branches “behind” the multi-storey drains must have an “inner Bend“ to divert the pressure flow outflow into the following open downpipe.

Calculate the required drainage for the main drainage (QrMain) and emergency drainage (QrNot) for the roof and the roof terrace using the online calculation.

Stream 1 main drainage

QrMain roof = 1,5 l/s
QrMain middle roof terrace= 0,9 l/s
QrMain lower roof terrace = 0.9 l / s

Stream 2 emergency drainage

QrEmergency roof = 1,5 l/s
QrEmergency medium roof terrace = 0,9 l/s
QrEmergency lower roof terrace = 0,9 l/s

Check whether the sum per stream (from step 5) is less than or equal to the maximum flow rate of the lowest roof terrace drain. The distribution of the inflow on the floors above can be distributed differently on the floors depending on the property. The decisive factor in this test is the sum at the lowest roof terrace drain.

Exceeds the sum of a stream with one DN 50 Pipe 4 l / s, that's the DUOSTREAM for high performance to be used with double pipe DN50 with up to 8 l / s.

Determine the height of the downpipes from the upper floor to the floor below, measured from the lower edge of the collecting tank to the middle of the horizontal warpage.

In order to be able to build up sufficient overpressure in the DN100 downpipe, the height of the downpipe used for the measurement from each floor to the floor below should be at least 2.5 m.

H1 is the height of the downpipe from the roof to the middle roof terrace.
H1 = 2.75 m.

H2 is the height of the downpipe from the middle roof terrace to the lower roof terrace.
H2 = 2.75 m.